Study of the Earth ’ s short - scale gravity field using the 4 ERTM 2160 gravity model

39 This paper describes the computation and analysis of the Earth's short-scale gravity field 40 through high-resolution gravity forward modelling using the Shuttle Radar Topography 41 Mission (SRTM) global topography model. We use the established residual terrain modelling 42 technique along with advanced computational resources and massive parallelisation to 43 convert the high-pass filtered SRTM topography – complemented with bathymetric 44 information in coastal zones – to implied short-scale gravity effects. The result is the 45 ERTM2160 model (Earth Residual Terrain modelled-gravity field with the spatial scales 46 equivalent to spherical-harmonic coefficients up to degree 2160 removed). ERTM2160, used 47 successfully for the construction of the GGMplus gravity maps, approximates the short-scale 48 (i.e., ~10 km down to ~250 m) gravity field in terms of gravity disturbances, quasi/geoid 49 heights and vertical deflections at ~3 billion gridded points within ±60 latitude. ERTM2160 50 reaches maximum values for the quasi/geoid height of ~30 cm, gravity disturbance in excess 51 of 100 mGal, and vertical deflections of ~30 arc-seconds over the Himalaya mountains. 52 Analysis of the ERTM2160 field as a function of terrain roughness shows in good 53 approximation a linear relationship between terrain roughness and gravity effects, with values 54 of ~1.7 cm (quasi/geoid heights), ~11 mGal (gravity disturbances) and 1.5 arc-seconds 55 (vertical deflections) signal strength per 100 m standard deviation of the terrain. These 56 statistics can be used to assess the magnitude of omitted gravity signals over various types of 57 terrain when using degree-2160 gravity models such as EGM2008. Applications for 58 ERTM2160 are outlined including its use in gravity smoothing procedures, augmentation of 59 EGM2008, fill-in for future ultra-high resolution gravity models in spherical harmonics, or 60 calculation of localized or global power spectra of Earth's short-scale gravity field. Graphical Abstract 65 66 67 68 Highlights 69 70  Residual gravity model ERTM2160 computed from the SRTM topography at 250 m 71 resolution 72  Supercomputing resources used for forward gravity modelling at ~3 billion points 73  Global short-scale RMS signal magnitudes are 1.6 cm for geoid, 11 mGal for gravity 74  Linear relation between terrain roughness and RMS gravity signal magnitudes found 75 76